Mixamo adding a weapon to character

Questions
,
1

Does anyone know how to add a weapon to an animated mixamo mesh? I added a weapon to my character in Blender and it plays fine but when I export it as a .glb and try to play the animation in Three.js the weapon just stays still and doesn’t update with the hands. I attached the .blend file if anyone wants to take a look.

I’m testing out the animation using the gltf loader https://gltf-viewer.donmccurdy.com/
terroist.blend (3.2 MB)

2

Does it have to be a weapon? Would a tool, toy or some other object do?

3

Yes anything will do. Just need to have the object in the hand when animating. Not sure why it work in Blender but not Three.js